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<title>Light and Optics - Brewster's Law - Physics 299</title>
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<h1><img src="ULPhys1.gif" height="50" width="189" align="texttop">
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<h1>Brewster's Law<br>
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<center><img src="celticbar.gif" height="22" width="576"> <br>
<br>
<font color="#ff0000"><i>"</i><i><span></span></i><i>If aliens
visit us, the outcome would be much as when Columbus landed in
America, which didn't turn out well for the Native Americans.</i><i><span></span></i><i>"</i></font><br>
<font color="#ff0000"><i>
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charset=windows-1252">
</i></font><font color="#ff0000"><i>
<meta http-equiv="content-type" content="text/html;
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</i></font> Stephen Hawking<br>
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<ul>
<li>By applying the boundary conditions for electromagnetic waves
striking the boundary between two media it can be shown that the
intensity of the reflected and refracted waves depend on the
polarisation of the incident wave.&nbsp; <br>
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<li>In particular, for unpolarised light incident on the boundary
at a specific angle, &#952;<sub>p</sub> , the reflected light
contains only one polarisation.&nbsp; When this occurs the
reflected and refracted light rays are at 90<sup>0</sup> to each
other, <br>
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<div align="center"><img alt="brewster eqn1"
src="lo_brewster_eqn1.jpg" height="58" width="156"><br>
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<ul>
<li>Using Snell's law we can show that,</li>
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<div align="center"><img alt="brewster eqn2"
src="lo_brewster_eqn2.jpg" height="86" width="390"><br>
<blockquote>
<div align="left">This relationship is known as <a
href="http://www.brewstersociety.com/brewster_bio.html"><img
alt="brewster" src="lo_brewster.jpg" height="128"
border="0" width="108" align="middle"></a><a
href="http://www.brewstersociety.com/kaleidoscope-university/sir-david-brewster/">Brewster's
</a> Law.<br>
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<div align="center"><img alt="brewsters fig1"
src="lo_brewster_fig1.jpg" height="297" width="405"><br>
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<li>For light incident on water (from air) we find that &#952;<sub>p</sub>=
53<sup>0</sup>.&nbsp; Thus, at this angle the light
reflected from the surface is (linearly)
polarised.&nbsp; If this reflected wave is viewed with
polarised sunglasses (which block this particular
polarisation), no reflective glare is observed -
allowing the observer to see clearly underwater.<br>
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<img src="netbar.gif" height="40" width="100%"><br>
<center>"<font color="#ff0000"><i><span class="bqQuoteLink">Outside
of a dog, a book is a man's best friend. Inside of a dog
it's too dark to read.</span></i><span></span><span
style="font-style: italic;">"</span></font><br>
<span style="font-style: italic; color: rgb(255, 0, 0);">
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</span> Groucho Marx<br>
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&nbsp;
<p><i>Dr. C. L. Davis</i><br>
<i>Physics Department</i><br>
<i>University of Louisville</i><br>
<i>email</i>: <a href="mailto:c.l.davis@louisville.edu">c.l.davis@louisville.edu</a>
<br>
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